Hybrid treatment systems--anaerobic ponds and trickling filters in Zimbabwe.

The most economic combination of unit treatment processes for a new sewage treatment works in Zimbabwe was found to be anaerobic ponds followed by trickling filters. The regulations governing irrigation with treated effluent permitted the omission of humus tanks or further treatment. Two stage anaerobic ponds are desludged by gravity through fixed sludge outlet pipework. Sludge is disposed of by irrigation of a Eucalyptus plantation. Novel features of the inlet works and pond outlets are also described. The works has functioned for eight years without major problems, but the assumption that humus tanks or settling ponds were not required may have been mistaken. The sludge removal system has worked well. Without the sludge pipework, it is estimated that desludging of the primary ponds would have been required after two years of operation, but they have now operated successfully for eight years. The combination of anaerobic ponds and trickling filters should be considered where land availability or site conditions make facultative ponds difficult or expensive to construct.

Double-blind randomized phase II study of hyperbaric oxygen in patients with radiation-induced brachial plexopathy.

BACKGROUND: Radiation-induced brachial plexopathy (RIBP) is an untreatable complication of curative radiotherapy for early breast cancer, characterized by chronic neuropathic pain and limb paralysis. Hyperbaric oxygen (HBO2) therapy is known to promote healing of tissue rendered ischaemic by radiotherapy, but is untested in RIBP. METHODS: Thirty four eligible research volunteers suffering from RIBP were randomized to HBO2 or control group. The HBO2 group breathed 100% oxygen for 100 min in a multiplace hyperbaric chamber on 30 occasions over a period of 6 weeks. The control group accompanied the HBO2 group and breathed a gas mixture equivalent to breathing 100% oxygen at surface pressure. All volunteers and investigators, except the operators of the hyperbaric chamber and the trial statistician, were blind to treatment assignments. The warm sensory threshold, which measures the function of small sensory fibres, was selected as the primary endpoint. FINDINGS: Pre-treatment neurophysiological tests were grossly abnormal in the affected hand compared to the unaffected hand in both HBO2 and control groups, as expected, but no statistically significant differences were noted in either group at any time up to 12 months post-treatment. However, normalization of the warm sensory threshold in two of the HBO2 group was reliably recorded. Two cases with marked chronic arm lymphoedema reported major and persistent improvements in arm volume for at least 12 months after treatment with HBO2. IINTERPRETATION: There is no reliable evidence to support the hypothesis that HBO2 therapy slows or reverses RIBP in a substantial proportion of affected individuals, although improvements in warm sensory threshold offer some suggestion of therapeutic effect. Improvement in long-standing arm lymphoedema was not anticipated, and justifies further investigation.

Outcome after treatment of neurological decompression illness is predicted by a published clinical scoring system.

BACKGROUND: After recompression therapy, some cases of neurological decompression illness (DCI) have a significant residual deficit. Boussuges et al. report a scoring system to predict sequelae using weighted historical and clinical indices at presentation which we applied to the British Hyperbaric Association (BHA) database of UK diving accidents, held at the Institute of Naval Medicine (INM). METHODS: A database search identified 234 cases of neurological DCI from the 2 yr, 1995-6. Of these, 217 case records contained sufficient data to apply the scoring system. Outcome was classified as severe sequelae (i.e., causing a functionally important deficit) or as mild/no sequelae. RESULTS: The median score in UK cases with severe sequelae was 13 (95% C.I. 11.5 to 14.5) and in cases with mild/no sequelae, 6 (95% C.I. 5.5 to 6.5). Significantly more cases with scores > 7 had severe sequelae than cases with scores < or = 7 (chi2, p < 0.0001). The sensitivity of a score > 7 (for severe sequelae) was 94% and the specificity was 65%. The positive predictive value of a score > 7 (for severe sequelae) was 18% and the negative predictive value of a score < or = 7 was 99%. CONCLUSIONS: When applied to the INM/BHA database a score of > 7 by this scoring system has a higher sensitivity and lower specificity for severe sequelae than reported by Boussuges et al. It has a higher predictive accuracy for successful outcome of treatment (99% vs. 89%) but a much lower predictive value for severe sequelae (18% vs. 86%). Convergence between this and other published scoring systems may allow derivation of a generic scoring system that could then be evaluated prospectively in multiple centers.

Acute carpal tunnel syndrome in a diver: evidence of peripheral nervous system involvement in decompression illness.

Conclusive evidence for involvement of the peripheral nervous system in decompression illness is lacking. We report a case of decompression illness associated with shoulder pain and the clinical features of median nerve injury at the wrist. Initial recompression and hyperbaric oxygen treatment produced prompt relief of all symptoms and signs, but carpal tunnel syndrome subsequently recurred. Nerve conduction studies confirmed median nerve conduction delay at the wrist. Repeat measurements after treatment with hyperbaric oxygen showed electrophysiologic improvement that was consistent with improvement in symptoms. We believe this is the first objectively substantiated case of injury to the peripheral nervous system caused by decompression illness.

Aspects of neurological decompression illness: a view from Bethesda.

A minority of divers with neurological decompression illness (DCI) fail to improve with recompression treatment. This is particularly seen in cases where features of severe spinal cord injury develop soon after surfacing. Haemorrhage into the spinal cord is implicated in the pathogenesis of these cases, and evidence is presented that supports the view that the bleeding coincides with shrinkage of autochthonous bubbles. The role of hyperbaric oxygen therapy in the treatment of spinal cord DCI is discussed with reference to possible benefit in ischaemia-reperfusion (I-R) injury. Similarities and differences between the tissue injury of dysbaric and conventional spinal cord injury are outlined. The implications of advances in drug therapy for conventional spinal cord trauma are considered in the context of their potential application to treat neurological DCI.

Pneumothorax as a complication of recompression therapy for cerebral arterial gas embolism.

The danger from pneumothorax in patients who undergo compression chamber treatment for cerebral arterial gas embolism (CAGE) following pulmonary barotrauma is frequently emphasized. Two cases of CAGE treated by recompression after submarine escape tank training (SETT) accidents are described. Both were complicated by bilateral pneumothoraces but the first case, treated on an air table, required thoracentesis in the chamber, whereas the second case, treated on an oxygen table, escaped the need for in-chamber thoracentesis despite large pneumothoraces. Review of similar Royal Navy and United States Navy SETT accidents suggests that the danger from pneumothorax during recompression treatment of CAGE victims may be overstated. Modern management on oxygen-based therapeutic recompression tables may significantly reduce the risk. Thoracentesis while under pressure should be reserved for cases developing symptoms or signs of tension pneumothorax. Treatment options for these cases are discussed and a decision algorithm is proposed.

Carbon monoxide poisoning: forgotten not gone!

Carbon monoxide causes one third of all poisoning deaths in Britain. In this paper a modern scheme for the assessment and management of victims of carbon monoxide poisoning is outlined, the importance of the direct cellular toxicity of carbon monoxide and the rationale behind hyperbaric oxygen therapy are discussed, and a list of currently available hyperbaric facilities is given.

Mercaptoethanol protects glutathione depleted cells.

Buthionine sulfoximine depleted the glutathione (GSH) level of mouse lymphoma L1210A cells in culture to 6% of control and killed the cells within 48 hours in medium supplemented with fetal calf serum or bovine serum albumin. Mercaptoethanol or alpha-thioglycerol but not GSH or cysteine added to the medium protected the cells from the effect of GSH depletion. Horse serum was also protective, and this effect was removed by dialysis over 65 hours and could not be restored by adding GSH. Mercaptoethanol alone had a protective action in the dialyzed sera. The results suggest that mercaptoethanol may act independently and perform the functions of GSH.